Boeing 757 operators are being strongly advised to ensure flexible hydraulic hoses in the landing-gear are maintained and regularly replaced, after instances of hydraulic failure.
The US FAA, in a newly-issued airworthiness bulletin, refers to “multiple events” in which the left-hand hydraulic system has been lost as a result of fatigue failure affecting the flexible hoses.
It highlights the runway excursion accident involving a Panamanian-registered DHL 757-200 freighter which suffered a left hydraulic system failure while climbing out of San Jose airport in Costa Rica on 7 April 2022.
The crew opted to return to San Juan, understanding that several systems – among them the left autopilot, autobrakes, certain spoilers and the nose-wheel steering – would be unavailable.
Although the initial touchdown on runway 07 was successful, with the crew maintaining directional control with differential braking and the right-hand thrust-reverser, the Costa Rican inquiry believes “muscle memory” reaction led to inadvertent simultaneous movement of the right reverse-thrust lever and the left engine thrust control.
This resulted in the aircraft’s sharply deviating to the right near taxiway D, and the crew lost control. The 757 travelled down a slope and suffered severe damage, including the separation of its empennage, although neither of the pilots was injured.
Investigators state that “material fatigue and stress” in a left-hand main landing-gear actuator hose initiated the hydraulic failure.
The FAA bulletin stops short of an airworthiness directive but states that, although flexible hoses are designed to cope with movement, repetitive cycles can degrade them.
Boeing issued a service letter to operators in March last year outlining best practices for hydraulic system maintenance, and specifically recommending initial replacement of older hoses in the main and nose landing-gear wheel wells – along with “pro-active repetitive replacements” to minimise failure risk.
In its bulleting the FAA advises all 757 operators to review this Boeing letter and carry out the measures listed.
